This invention relates to a dispensing gun for dispensing viscous materials which may be of a thick liquid nature or a pasty nature, for example a mastic caulking material.
Such viscous materials are sometimes supplied in a cartridge which, when in use, is open at one end and has a discharge orifice at the other end. By suitably advancing a plunger into the cartridge from its open end, the viscous material can be dispensed from the discharge orifice.
Such guns generally comprise means such as a tube for holding a cartridge and a body portion similar to a pistol and comprising a main portion in which a reciprocating rod is mounted and a butt portion by which the gun can be held. There is a trigger which depends from the body portion alongside the butt portion and which, when it is squeezed, advances the rod. An example of such a construction is found in British Pat. No. 1,264,311 of Patrick C. Cox, published Feb. 23, l972. In this gun, as with the majority of such guns produced hitherto, the stock comprising the body and butt is formed as a complex die casting and the trigger is formed as another complex die casting. The cost of dies for such castings is high and the cost of producing objects from such dies is also high since casting has to be at comparatively high temperatures and relatively expensive alloys must be used. Moreover, such die castings tend to be brittle and, while they can be designed to be aesthetically pleasing, this property is of less importance than strength and long life when it is realised that such dispensing guns are used mainly in industrial and construction environments.